Pile driving mandrel



Feb. 1, 1966 P. K. DAVIS 3,232,061

PILE DRIVING MANDREL Filed Oct. 5, 1962 ATTORNEYS United States Patent 3,232,061 FILE DRIVING MANDREL Paul K. Davis, 425 Kittyhawh Road, Alameda, Caiif. Filed Oct. 3, 1962, Ser. No. 228,087 Claims. (Cl. 61-5312) This invention relates generally to a pile driving mandrel, and more specifically to a mechanically expandable mandrel for driving pile shells into the earth.

It is customary in the construction industry to utilize relatively thin walled pipe as pile shells which are driven into the earth to act as forms or casings for concrete piles. Since such a pile shell is not sufficiently strong to withstand the forces applied to it by the pile driving apparatus, it is necessary to support the pile shell for driving apparatus, it is necessary to support the pile shell for driving by means of a mandrel. Such mandrels are generally either mechanically or hydraulically actuated between an expanded condition for driving the shell and a collapsed condition to permit the mandrel to be inserted into a pile shell and released therefrom after driving. i

The complexity and resultant high cost of hydraulically actuated mandrels and the frequent breakdowns sustained by prior known mechanically actuated mandrels have plagued the construction industry for some time.

Therefore, it is an object of the present invention to provide a pile driving mandrel of extremely simplified, rugged and compact construction.

It is another object of the present invention to provide a mechanically expandable pile driving mandrel wherein the tendency of the mandrel to. buckle due to driving impact is virtually eliminated.

Yet another object of the present invention is to provide a mechanically expandable pile driving mandrel requiring minimal movement of the. expanding mechanism between driving and releasepositions.

A still further object of the present invention is to provide a mechanically expandable pile driving mandrel which is securely expanded and braced against the inner surface of the pile shell by the driving impactupon the driving head and is quickly and easily releasable from the pile shell by pulling upwardly on the driving head.

Still another object of the present invention is to provide a pile driving mandrel which is capable of withstanding sustained driving operations with a minimum of maintenance. 7

These and other objects and advantages of the present invention will become more readily apparent in the following description of the invention taken in conjunction with the accompanying drawing, in which:

FIG. 1 is an elevational view, partly broken away to show internal details, of the mandrel of this invention during the driving operation;

FIG. 2 is an elevational view similar to FIG. 1, but as seen from a right angle thereto, of the upper portion of the mandrel in condition for being withdrawn from the pile shell;

FIG. 3 is a transverse sectional view taken along the line 3-3 of FIG. '1;

FIG. 4 is a transverse sectional view taken along the line 44 of FIG. 2;

FIG. 5 is an elevational view, similar to FIG. 2, partly broken away to show internal details, of a modification of the connection between the driving head'and mandrel;

FIG. 6 is a perspective view of a portion of the modification shown in FIG. 5, showing the connecting link in detail.

Generally, the mandrel of this invention comprises an elongated, rigid core of smaller outside diameter than the inside diameter of the pile shell to be driven. A plurality of elongated shoes of substantially the same length as the core extend in generally parallel relation to the core and are arranged circumferentially thereof. Each such shoe is connected to the core by a plurality of transverse links each longer than the radius of the pile shell and extending diametrically through the core and spaced longitudinally thereof.

A driving head of a conventional pile driving apparatus is connected to the upper end of the core for imparting driving impact to the core to extend the shoes laterally into tight frictional engagement with the inner surface of the pile shell and thereby drive the pile shell into the earth. Thus, a rigid, integral driving relationship is established between mandrel and pile shell to support the pile shell during the driving operation. When the pile shell is driven to the desired depth, the driving head is pulled upwardly to collapse the shoes relative to the core to permit the mandrel to be withdrawn from the pile shell.

Referring now to FIG. 1, there is shown a conventional, relatively thin walled pile shell 10 having a bottom or cap 10a, and which is partially driven into the earth, indicated generally at 11, by means of the mandrel which is indicated generally at 12. The mandrel 12 comprises an elongated, rigid core 13 of smaller outside diameter than the inside diameter of the pile shell 10, and having a cross-shaped cross section formed by two web members 14, 15 which are integrally connected together along their respective longitudinal axes normal to each other.

A conventional driving head 16 is connected to the upper end of the core 13 by means of a clevis 17 which is mounted on the top of the member 15 by means of a bearing 18 through which is inserted a pin 19. The pin 1h may extend through webs 14 and is removably secured therein in a conventional manner. This arrangement allows the driving head 16 to be securely attached to the core 13, and yet be conveniently and easily removed therefrom as desired.

Four shoes 20 are mounted peripherally of the core 13 in parallel relation thereto and are adapted to be laterally expanded therefrom for frictionally engaging the inner surface of the pile shell 10. Each shoe 24 is movably connected to one of the webs 14, 15, adjacent one of its respective laterally extending edges by a plurality of links, to be subsequently described. The shoes 20 are of substantially the same length as the core 13 so that during a driving operation the upper ends of the shoes 20 abut against the underside of the driving head 16, and the lower ends of the shoes 21 are fiush with the lower end of the core 13 to bear directly against the bottom 10a of the pile shell 10.

Thus, the driving impact is distributed through the driving head 16 over the entire cross section of the mandrel 12 and imparted uniformly over the portion of the inner surface of the pile shell 10 in engagement with the outer surfaces of the shoes 20 due to the tight frictional engagement between the shoes 29 and the pile shell, with the result that the pile shell and mandrel are driven as a unit into theground.

The elongated shoes 29 are preferably integrally formed to a generally U-shaped cross section (FIG. 3), with the outer surfaces thereof curved to generally correspond to the curvature of the inner surface of the pile shell. When the mandrel is to be used for driving corrugated pile shells, as illustrated in FIGS. 1 and 2, a plurality of friction gripping beads 21 may be securely fastened, as by welding, to the outer surface of the shoes 20 to extend along at least the lower half of the length thereof for providing positive frictional engagement between the shoe and the shell wall. The rear portion of each shoe 20 terminates Patented Feb. 1, 1966 u in a pair of inwardly extending flanges 22 for receiving therebetween the outer edges of webs 14, 15.

The following description relating to the connection of the linkages 23 to the core 13 and to the shoes 20 pertains to one shoe 20 and the linkages associated therewith, as it will be understood that the shoes operate independently of each other and that each of the shoes 20 is connected to the core 13 and actuated by the linkages 23 in a similar manner. It will also be understood that the number of linkages 23 for each shoe 20 and the spacing thereof along the core 13 depends upon the length of the mandrel.

Each of the shoes 20 is connected to the core 13 by means of a plurality of transverse linkages 23 which are spaced at intervals longitudinally of the core 13 and shoe 20 and are of a length which is greater than the radius of the pile shell 10. Each linkage 23 comprises a pair of spaced parallel links 24 which extend on opposite sides of one of the web members, as for example, web 15, as seen in FIG. 3.

The webs 14, 15 each have a plurality of transversely extending pairs of slots 25 therein preferably spaced at approximately equal intervals longitudinally thereof adjacent the juncture of the webs. Each pair of links 24 extends through a pair of slots 25 to enable the links 24 to extend the width of web 15. One end of the pair of the links 24 is pivotally connected to web 15 at a point thereon adjacent the edge opposite the shoe 20. The other end of the pair of the links 24 extends beyond the other edge of web 15 to be received between the flange members 22 of the shoe 20 for pivotal connection thereto by a pin 27.

Each edge of webs 14, 15 has a notched-out portion 28 therein (FIG. 2) adjacent the connection of each pair of links and shoe to thereby provide a pair of spaced end abutments 29, 30. Links 24 are of suflicient length to position pin 27 within the notched-out portion 23 for movement between the abutments 29, 30. The abutments 29, 3% thereby limit the axial displacement of said shoes relative to said core. It will be noted in FIG. 2 that the abutment 31 is on the same horizontal plane as the upper surface of the pin 26. Thus, when the upper surface of the pin 27 engages the abutment 30, the linkage 23 will be in a generally horizontal or locking position as shown in FIG. 1.

Referring now to FIG. 2, the mandrel 12 is shown in its collapsed or release condition as it appears when being initially inserted into the pile shell prior to a driving operation, and also upon subsequent withdrawal of the mandrel from the pile shell. The shoes 20 are normally displaced downwardly relative to the core 13 by their weight until the pin 27 engages the abutment 29 in the notched-out portion 28 to thereby limit such downward movement. The mandrel 12 is inserted into the pile shell 10 until the lower ends of the shoes 20 are brought to bear against the bottom 19a thereof. The relatively greater weight of the core 13 plus the driving head 16 will cause the core 13 to be displaced downwardly relative to the shoes 20 until the lower end of the core almost engages the bottom 10a of the pile shell. As the core moves downwardly, the linkages 23 will be pivoted to thereby extend the shoes 20 laterally into engagement with the inner surface of the pile shell 10.

The linkages 23 are preferably of such length that when the shoes 20 are fully extended the outer diameter of the mandrel 12 is slightly larger than the inner diameter of the pile shell 10 to insure tight frictional engagement between the outer surfaces of the shoes 20 and the inner surface of the pile shell. This arrangement prevents the lower end of the core 13 from contacting the bottom 10a of the pile shell by virtue of the mere weight of the core and driving head alone. Thus a driving impact on the driving head 16 is generally necessary to fully seat the mandrel within the pile shell in order to thereby es-,,

tablish a driving relationship between the mandrel and the pile shell.

In this driving relationship the mandrel is in the position shown in FIG. l, wherein the lower ends of the shoes 20 and the core 13, respectively, are flush and in engagement with the bottom 10a of the pile shell; the upper ends of the shoes 26 and the core 13, respectively, are in engagement with the underside of the driving head 16; the shoes 20 are in tight frictional engagement with the inner surface of the pile shell; and the linkages 23 are all locked in a horizontal, or substantially horizontal, position to thereby maintain the driving relationship during a driving operation. It will be obvious that the shoes 20 and the linkages 23 cooperate in the manner of toggle levers to thereby lock the shoes 20 against the inner surface of the pile shell when the levers are in the horizontal position.

In the above described driving relationship, the driving impact is almost completely absorbed by the core 13 and the shoes 20 with very little being transmitted to the links 24. However, the support which is afforded the linkages 23 by virtue of the links 24 thereof extending along either side of the webs 14 and protects the linkages from shear and torque forces resulting from the small amount of driving impact which may be transmitted to them.

When the driving operation is completed and it is desired to remove the mandrel from the pile shell, the mandrel is collapsed by pulling upwardly on the driving head 16 to pivot the linkages 23 and allow the shoes to be released from engagement with the inner surface of 4 the pile shell.

. therebetween for a minimum amount of movement between driving and collapsed positions. The larger the cross sectional area of the core, the greater strength and rigidity the mandrel will have to resist buckling due to driving impact, and it is preferred to have a core of maximum cross section which will still allow the mandrel to fit within the pile shell.

By extending each of the linkages 23 through the core on the diameter of the pile shell, the optimum mechanical advantage available is realized by virtue of the length of the linkages 23 which results in the maximum frictional engagement being created between the shoes 20 and the inner surface of the pile shell. This frictional engagement and the direct transmission of the driving impact to the bottom 10a of the pile shell through the core 13 and the shoes 20 provide the mandrel 12 with the integral rigidity and structural strength of a solid shaft during a driving operation. The simplicity and reliability of the toggle lever relationship between the shoes 20 and the linkages 23 in combination with the aforementioned rigidity and strength provide a pile driving mandrel which is far superior to mandrels heretofore known.

An alternate means of coupling the driving head to the mandrel is shown by the modification illustrated in FIG. 5. A generally cylindrical extension member is securely attached to the underside of the driving head 16 as by welding, and is preferably larger in diameter than the outer diameter of the pile shell 10.

A generally cylindrical extension member 132 of the same diameter as the core 13 is securely attached to the top of core 13, as by welding, in axial alignment with member 100 to act as an extension of the core.

The driving head 16 and member 1% are removably connected as a unit to core 13 and member 162 by means of an elongated connectiing link 1103. An elongated, generally rectangularly shaped aperture 104 extends axially through members 100, 102 for receiving therein link 103. Aperture 104 is of sufficient cross sectional area and length to permit link 103 to move freely therein along the axes of members 100, 102.

Link 103 has a pair of spaced, elongated slots 105, 1% extending laterally therethrough, and is retained in aperture 104 by a pair of spaced, parallel pins 107 and 108. Pin 107 extends diametrically through member 100 normal to the axis thereof and is received within slot 105 in link 103. Pin 108 extends diametrically through member 102 normal to the axis thereof and is received Within slot 106 of link 103. Pins 107 and 108 are securely yet removably retained within members 100 and 102 respectively, in a conventional manner to prevent their being inadvertently dislodged therefrom during operation yet to permit their removal when desired.

When a driving relationship is established between the driving head and mandrel, as previously described, the member 100 is seated on the top of member 102 in abutting relation thereto, and the outer perimeter of the underside of member 100 is engaged with the tops of shoes 20 and the pile shell for imparting the driving impact directly thereto. The pins 107 and 108 are spaced at sufiicient distance apart to allow the link 103 to be carried loosely on said pins within aperture 104 during a driving operation (FIG. 6) due to the elongation of slots 105, 106. Thus the pins 107, 108 are protected against shearing resulting from driving impact. The mandrel is retracted from the pile shell after a driving operation by pulling upwardly on the driving head 16. Such upward pulling will space the member 100 from member 102 until link 103 engages pins 107, 108 (FIG. 5) to pull the mandrel upwardly, thereby collapsing the shoes 20, as previously described.

While the mandrel of this invention has been described with specific reference to the embodiments thereof illustrated in the accompanying drawing, it will be understood that various modifications and changes in the mandrel may be made within the skill and understanding of persons skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims. For example, the central core is not intended to be limited to one having a cross-shaped cross section, but may have a circular or any other shaped cross section as contemplated within the spirit and scope of the invention.

I claim:

1. A mandrel for use in driving relatively thin walled pile shells, comprising:

(a) an elongated core having a central, longitudinal axis and a cross section providing a plurality of symmetrically disposed web portions projecting outwardly away from said axis, the angles between said web portions being less than 180 dgrees;

(b) said web portions having slots extending transversely therethrough;

(c) an equal plurality of symmetrically disposed elongated shoes extending substantially parallel to said core, each of said shoes being opposite said axis from a respective web portion and extending outwardly away from said axis a distance greater than the projection of said web portion;

(d) a plurality of transverse links connecting each said shoe at spaced points along its length to said core for parallel movement of said shoes toward and away from said core by relative axial displacement of said core and shoes; (e) each said link being pivotally connected at one end to a web portion at a point substantially spaced from said axis and extending transversely through a said slot to a pivotal connection to its respective shoe on the opposite side of said axis;

(f) the upper ends of said core and said shoes being adapted to support a driving head in driving engagement therewith.

2. A mandrel for use in driving relatively thin walled pile shells, comprising:

(a) an elongated, central core of substantially the same length as a shell to be driven and having a cross-shaped cross section providing a pair of webs normal to each other;

(b) said webs having a plurality of transversely extending pairs of slots therein spaced at equal intervals longitudinally thereof;

(c) an elongated shoe adjacent each of the opposed outer edges of each of said webs extending substantially parallel to and of the same length as said core;

(d) a plurality of linkages connecting each said shoe at spaced points along its length to said core for parallel movement of said shoes into and out of frictional driving relation with the wall of such pile shell;

(e) each of said linkages including a pair of links on opposite sides of one of said webs pivotally connected at one end to their respective shoe and extending through a. pair of said slots in the other of said webs to a pivotal connection to said one web at a point thereon remote from said respective shoe.

3. The mandrel of claim 2, in which:

(f) each said shoe having a generally U-shaped cross section providing a pair of inwardly directed flanges; and,

(g) said outer edges of said webs being received tween said flanges.

4. The mandrel of claim 2, in which:

(f) each said shoe having a generally U-shaped cross section and the outer surface thereof conforming to the curvature of the wall of such pile shell.

5. The mandrel of claim 4 including:

(h) said outer edges of said webs having a notch adjacent the connection of each said linkage and each said shoe providing a pair of spaced abutments at the ends of said notch;

(i) a pin connecting said one end of each of said pairs of links to said flanges of their respective shoe;

(i) said pin being received in said notch for movement between said abutments to limit the movement of said shoes.

References Cited by the Examiner UNITED STATES PATENTS 977,356 11/1910 Withrow 6153.72 X 1,164,435 12/1915 Wallett 6153.72 1,173,806 2/1916 Johnson 61-53.72 1,865,653 7/1932 Upson et al. 61-53.72 1,912,089 5/1933 Moe 6153.72 X

CHARLES E. OCONNELL, Primary Examiner.

JACOB SHAPIRO, EARL I. WITMER, Examiners. 

1. A MANDREL FOR USE IN DRIVING RELATIVELY THIN WALLED PILE SHELLS, COMPRISING: (A) AN ELONGATED CORE HAVING A CENTRAL, LONGITUDINAL AXIS AND A CROSS SECTION PROVIDING A PLURALITY OF SYMMETRICALLY DISPOSED WEB PORTIONS PROJECTING OUTWARDLY AWAY FROM SAID AXIS, THE ANGLES BETWEEN SAID WEB PORTIONS BEING LESS THAN 180 DEGREES; (B) SAID WEB PORTIONS HAVING SLOTS EXTENDING TRANSVERSELY THERETHROUGH; (C) AN EQUAL PLURALITY OF SYMMETRICALLY DISPOSED ELONGATED SHOES EXTENDING SUBSTANTIALLY PARALLEL TO SAID CORE, EACH OF SAID SHOES BEING OPPOSITE SAID AXIS FROM A RESPECTIVE WEB PORTION AND EXTENDING OUTWARDLY AWAY FROM SAID AXIS A DISTANCE GREATER THAN THE PROJECTION OF SAID WEB PROTION; (D) A PLURALITY OF TRANSVERSE LINKS CONNECTING EACH SAID SHOE AT SPACED POINTS ALONG ITS LENGTH TO SAID CORE FOR PARALLEL MOVEMENT OF SAID SHOES TOWARD AND AWAY FROM SAID CORE BY RELATIVE AXIAL DISPLACEMENT OF SAID CORE AND SHOES; (E) EACH SAID LINK BEING PIVOTALLY CONNECTED AT ONE END TO A WEB PORTION AT A POINT SUBSTANTIALLY SPACED FROM SAID AXIS AND EXTENDING TRANSVERSELY THROUGH A SAID SLOT TO A PIVOTAL CONNECTION TO ITS RESPECTIVE SHOE ON THE OPPOSITE SIDE OF SAID AXIS; (F) THE UPPER ENDS OF SAID CORE AND SAID SHOES BEING ADAPTED TO SUPPORT A DRIVING HEAD IN DRIVING ENGAGEMENT THEREWITH. 